1. Field of the Invention
The present invention relates to the medical field and particularly to orthopaedics and traumatology for the correction of limb bone deformities, disorders and deficiencies. More particularly, the invention relates to an implant or staple and method for repairing bones and/or correcting limb inequality and most preferably the invention relates to methods and staples for correcting bone deficiencies such as abnormal curvatures by suppressing and/or inducing the growth of the bone mass and/or the epiphyseal plate in the bone. Even most particularly the invention relates to a distraction staple and method for correcting abnormally curved spinal columns by distracting the vertebrae at the concave side of the column and promoting the growth of the end plate or epiphyseal plate at the concave side. Additionally, the invention relates to staples with enhanced osseous integrating means capable of being easily removed from the bone even once integrated. Furthermore, the invention relates to staples for preventing the perichondrium and the periosteal vascular ring from damage when installing the staple into the bone.
While more specific reference to disorders in the spinal column control and/or will be made in the present disclosure and drawings, the bone implant and methods of the invention are not restricted to this specific application but they may be applied to any other field where a prosthesis, a fixation device, a correction device, etc. is to be secured into a bone, proximal bones or a broken bone for correction and/or reparation purposes. In addition, the term “patient” is applicable either to animals or human beings.
2. Description of the Prior Art
Length discrepancies and angular deformities of the limbs are quite frequent among children and provoked by several causes such as congenital, post-trauma, post-infection, oncologic causes, etc. The need exists for correcting these abnormalities because of function and aesthetic reasons. The treatment of some of these childhood deformities is based on the concept of mechanically suppressing growth.
Bone staples are well known in the orthopaedics and traumatology, such as in techniques for correcting angular deviations of limbs, genu valgum for example, by unilateral restriction of the growth plate.
For correcting angular deviations the mechanical suppression can be obtained by temporary using metal staples across the growth plate, at unilateral locations, at the convex side of the deformity, for example. The staples are removed once the correction has been reached.
For correcting length abnormalities, the lengthening of the bone is obtained by using an external fixator and the shortening of the limb is obtained by arresting or suppressing the growth plate at even locations around the bone.
The technique of mechanical suppression by temporary using an external fixator is carried out by installing the fixator in the limb, on the concave bone side, for producing a slow stretching of the growth plate. This mechanical technique is known as epiphyseal distraction.
More precisely, epiphyseal distraction is a surgical technique that is widely used to lengthen an abnormal bone or correct physeal deviations prior to growth plate closure. This technique, also called “chondrodiatasis” , involves slow, gradual, symmetric distraction of the growth plate. The term “hemichondrodiatasis” , on the other hand, is used to refer to the technique of asymmetric distraction of the growth plate for correction of epiphyseal-diaphyseal deviations.
Since the use of external fixators for the above described mechanical suppressing techniques has shown to be expensive as well as traumatic and cumbersome for the patient, and the fixator leaves unsightly scars, the use of this device has not widely and intensively imposed. It would be desirable to use staples for these techniques, however, the staples are affected by several disadvantages and drawbacks that caused them to be not widely imposed in the medical field.
As it was stated above, angular deviations or deformities and length discrepancies of the limbs, for example, are often treated with staples. After staples are placed across a growth plate, further growth of this plate increases the pressure on the inner surfaces of the staple legs. This increased pressure, which has been measured about 1 Mpa, slows bone growth within and near the staple, i.e. in the region between the legs, and, simultaneously, forces the staple legs apart. This pressure from the cartilage plate, together with the legs moving away from each other, causes the legs to be extruded and expelled out from the bone thus loosing the grip in the bone.
Another drawback the physicians have found with the use of staples is that the same do not work satisfactorily because the bone growth is not restarted afterwards, thus producing the appearance of opposite deformity due to the constant growth of the cartilage of the side that was not operated upon. An explanation for this effect is that, presumably, a damage is inflicted on the perichondrium or the perichondrial vessels when the staples are inserted into physis. Generally, the staples are provided with reinforcing squares. at the inner side thereof, that is at the inner corners formed by the connection between the cross bar and legs. As the staple is hammered up to abutting the external surface of the bone, the reinforcements, as well as the flat bridge or cross bar enter into contact with the growth plate and damage the perochondrium and the perichondrial vessels, this being the cause of the undesired epiphysial arrest.
As indicated above in connection with one of the drawbacks of using staples, the pressure exerted by the growing cartilage plate causes the staple legs to open, extrude and slide out of the bone. Many staples of the prior art has attempted to prevent the staple from sliding out the bone by providing the staple legs with barbs or protrusions to enhance the anchoring of the legs into the bone mass. However, when the deformation has been corrected and the temporary staple must be removed from the bone, the anchorage of the legs into the growing bone mass, desired at the time the stable must be retained into the bone, is a bar or obstacle at the time the staple must be removed. In effect, this firm osseous anchorage prevents the staple from being easily removed by normal forces and operations.
Another aspect related to the bone malformations or disorders is the correction of abnormal curvatures in spinal columns, such as scoliosis. There are several devices, systems, implants and staples for connecting to the vertebrae to exert a force or combination of forces to urge the column and bring the same as close as possible into its normal curvature.
U.S. Pat. No. 6,325,805 to Ogilvie, et al. discloses a shape memory alloy staple comprising a cross bar with two or more prongs having a memorized shape wherein the prongs are angled towards one another and a deformed shape wherein the prongs are substantially parallel. This staple is for implanting in a couple of proximal vertebrae with said prongs in said deformed shape and the cross bar spanning the intervertebral disc with the purpose of exerting a compression force on the vertebrae. The fact of retaining a portion of the spine while permitting the growth of another part may operate successfully to correct the abnormal curvature of the spine, the final result is that the entire growth of the column is restricted and the column results, after the period of time involved in the treatment, shorter that it should be after the same period of time without any retention.
In order to prevent the restriction on the normal growth of the spine, other systems have been based in the distraction of the vertebrae instead of compressing the same. U.S. Pat. No. 6,921,403 to Cragg, et al. discloses a method and apparatus for spinal distraction and fusion wherein an axial bore is created in the spine up to the targeted vertebrae to be treated. An axially-extending rod with appropriate threads is inserted into the axial bore and the rod is extended to increase the distance between the two proximal vertebrae. While no compression is made the distraction is obtained by employing complex, cumbersome and dangerous systems.
U.S. patent application Ser. No. 10/768,797, published under No. US 2005/0171539 A1, to Braun, et al. discloses an implant simpler than the above Cragg's apparatus. Braun discloses a flexible body that is fixed at the ends thereof to respective fasteners which in turn are fixed to two proximal vertebrae with the flexible body extending intervertebrally between the two vertebrae. Before connecting to the two fasteners the flexible body is compressed in order to exert a distraction force between the fasteners. Since the fasteners are fixed to the vertebrae with the flexible body in said compressed state, the fasteners will transmit to the vertebrae the corresponding distraction force exerted by the flexible body. While this system is simple, it consists of at least three parts which is a drawback when it is working in a most sensitive area like the spinal column and, particularly when as smallest as possible tools are desired to be employed in the intervention. In addition, the use of fasteners, such as screws, is less and less preferred for the patient security. Another drawback of Bauer's system, which is not less important, is that the implant is attachable to the concave side of the spinal column with the undesired result that not only the concave side is distracted but also the convex side. In deed the growth of the vertebrae end plates at the convex side are inconveniently promoted with the final result of an abnormally elongated spine.
It would be therefore desirable and convenient to have a staple capable of being easily installed and implanted as well as a method for effectively correcting a spinal column that is out of its normal curvature without restricting and/or abnormally affecting the natural growth of the vertebrae.